A Review of the Transient Process and Control for a Hydropower Station with a Super Long Headrace Tunnel

Abstract

The hydropower station with a super long headrace tunnel is a significant development type for hydropower energy. By constructing a super long headrace tunnel, the huge natural water fall head can be utilized to generate more electricity. With the development of hydropower energy, a hydropower station with a super long headrace tunnel becomes more and more competitive. Compared with a hydropower station with a short headrace tunnel, the transient process and control for a hydropower station with a super long headrace tunnel is much more complicated and becomes an intractable challenge. It is well known that the transient process and control is the basis of the design and operation of a hydropower station. To overcome the challenge of the transient process and control, much research has been carried out. This paper provides a systematic review on the latest research progress of the transient process and control for hydropower stations with a super long headrace tunnel. Firstly, two key issues for the transient process and control, i.e., hydraulic design optimization of the surge tank and operation control of unit, are illuminated. Secondly, for both single surge tanks and surge tanks with special types or combinations, the hydraulic design optimization methods are described. The most disadvantageous design and advantageous operation of surge tanks under combined operating conditions are discussed. Thirdly, the stability and regulation quality of the hydro-turbine governing system under isolated and grid-connected operation conditions are presented. Finally, some trends and recommendations for future research directions are made. A research thought for establishing the complete theory and application system of the transient process and control for hydropower stations with a super long headrace tunnel from the perspective of multi-slice and multi-scale is proposed.

Analysis of the Power Fluctuations Caused by the Unstable Flow in the Trifurcation of Multi-Turbine Diversion Systems with Common Penstock in Hydropower Units

“…where n is the rotor speed. For example, the guide vane opening α of unit 1 is 19.3 mm, and the maximum value of n 11 , which is 70.96 r/min, can be calculated by Equation (4). With the values of α and n 11 known, the values of Q 11 and η, which are 820 L/s and 93.3%, can be obtained using the comprehensive characteristic curve chart.…”

“…The stable operation of hydropower units is essential to the power system. However, stable operation and good regulation performance have become challenges for hydropower stations with a long-distance headrace tunnel and high water head [4]. Faults occur at a higher frequency when the multi-turbine hydraulic coupled division system with a common penstock is adopted [5].…”

“…The long-distance headrace tunnel has been adopted widely to obtain a high working water head in hydropower stations [6]. However, it also leads to an extremely large flow inertia in the tunnel [4]. In addition, the water hammer, a kind of typical pressure fluctuation phenomenon, has become more serious than before.…”

Nonlinear Disturbance Decoupling Control for Hydro-Turbine Governing System with Sloping Ceiling Tailrace Tunnel Based on Differential Geometry Theory

“…With the development of the theory of a nonlinear dynamic system and the theory of nonlinear system control, such as fuzzy control [8], bifurcation and chaos control [9,10], nonlinear decoupling control based on differential geometry theory [11,12], sliding mode control [13], artificial neural network control [14], particle swarm optimization algorithm [15], artificial sheep algorithm [16], fractional order PID control [17], nonlinear predictive control [18,19] and nonlinear H ∞ control [20], and the improvement of the calculation and simulation capability of computer, now it is possible to study this special nonlinear dynamic system and design proper advanced control strategies. The nonlinear control methods in [8][9][10][11][12][13][14][15][16][17][18][19][20] are widely used in dynamic systems, such as mechanic and power systems. As an intelligent method, the fuzzy logic controller is widely used in industrial processes due to its inherent robustness [8].…”

“…The fractional order PID control is based on the fractional calculus theory and has been applied into some different fields in the past few years [17]. Nonlinear predictive control provides a flexible solution for the control of nonlinear [18,19]. The nonlinear H ∞ control theory has the capacity to cope with unknown disturbances [20].…”